Electronic mail (email) is the transmission of messages or computer files between computers that are connected to the Internet or some other communications network. Typically, email messages contain text, but non-text files, such as graphic images and sound files as attachments, can also be sent. Because emails are easy and inexpensive to send, many commercial advertisers are resorting to spam mail. Spam is another name for unsolicited electronic junk mail or junk newsgroup postings. More specifically, spam by email involves sending identical or nearly identical electronic messages by email to thousands (or millions) of recipients. A spammer is someone who sends out significant quantities of email advertisements, promotions, or scams that are unsolicited by the receiver of the spam.
Often times, spam email lists are created from email addresses harvested from Usernet postings or web pages, discussion boards and groups, databases, or are simply guessed by using common names and domains. There are also hundreds of companies that are willing to sell compact disks filled with millions of valid email addresses. The ease of spammers in obtaining valid email addresses makes it likely that many people with an active email account will be spammed.
On the individual scale, spam is problematic because it is often an unwanted intrusion on the recipient's time, mailbox space, and resources. For many Internet Service Providers, spam is considered to be a great financial drain and an impediment to Internet access because it can clog available bandwidth. However, because the Internet is a public network and because spamming can be extremely lucrative to the spammer, even when the response rate is very low, the practice is hard to stamp out.
Aside from email, it is believed that spam will infiltrate its way into other communication formats such as Voice over Internet Protocol (VoIP) and instant messaging (IM). VoIP is a way of utilizing the Internet and/or intranets for telephone conversations. IM is used to send messages back and forth through the Internet to a specific user, or between specific users. Because VoIP is usually significantly less expensive than typical long distance calls and IM can facilitate rapid communication between users, both VoIP and IM are gaining wider acceptance.
In the future, as VoIP and IM become mainstreamed, they will also suffer from spam problems such as unsolicited commercial phone calls over VoIP (Spam over Internet Telephony, SPIT) and unsolicited instant messaging (Spam over Instant Message, SPIM).